1. Field of the Invention
The present invention relates to a novel branched polycarbonate and a process for producing the same. More particularly, the present invention relates to a branched polycarbonate which is excellent in qualities such as heat stability, resistance to corrosion of molds, color tone and the like, and a process for producing the same.
2. Description of the Related Arts
As the process for producing polycarbonate (hereinafter referred to as PC), a method of directly bringing an aromatic dihydroxy compound such as bisphenol A into reaction with phosgen (the interfacial method), and a method of transesterifying an aromatic dihydroxy compound such as bisphenol A and a carbonic ester such as diphenylcarbonate in molten state (the melting method) are generally known. Among PCs obtained by such methods, linear PCs generally need improvement in molding properties such as melt elasticity and melt strength. For improving the molding properties, branching of PC by copolymerization of a polyfunctional organic compound is proposed, for example, in Japanese Patent Publications Showa 44(1969)-17149, Showa 47(1972)-23918 and Showa 60(1985)-11733.
However, when a branched PC is produced by using a conventional branching agent by the interfacial method, the branched PC obtained is inferior in heat stability and, moreover, causes a problem that molds are corroded. On the other hand, when a branched PC is produced by using a conventional branching agent by the melting method, the branched PC obtained is again inferior in heat stability and, moreover, causes a problem that color tone is inferior.